Chlorine gas in Submarines

[Baluncore]

Submarines that had lead acid batteries and were depth charged during WW1 or WW2 sometimes produced chlorine gas inside the submarine. Was that because;
1. Broken batteries leaked sulphuric acid into the bilges where sea water with NaCl had accumulated, or;
2. Leaking seawater flooded the battery compartment and the NaCl brine was hydrolysed between the battery terminals.

 

[Vanadium 50]

The latter.

If you are interested in such things, you might want to read about the USS Squalus.

 

[Baluncore]

The latter.

How do you know it can not be the first under different circumstances ?

The USS Squalus was clearly a case of sea water flooding the battery compartment. Electrolysis is highly probable, but so is mixing of battery electrolyte with sea water.
I am interested because of the many unexplained stories told. Such as in WW1, no leak in the hull, but broken battery cases that spilled electrolyte into the bilges and produced chlorine gas. It seems to me that there is no electrolysis cell in that scenario.
The fog of war and deliberate misinformation tend to hide the truth.

 

[Baluncore]

How about the following two reactions.

Mix battery acid with sea water to produce hydrochloric acid.
H₂SO₄ + 2 NaCl = 2 HCl + Na₂SO₄

Then use lead dioxide from the battery plate as an oxidiser to release chlorine gas.
4 HCl + PbO₂ = Pb + 2 H₂O + 2 Cl₂

That could produce chlorine gas without the hydrolysis of sea water between battery conductors.